1. Field of the Invention
The present invention relates to an active suspension apparatus for a vehicle, and more particularly, to an active suspension apparatus for a vehicle, which supplies a fluid to actuators disposed on wheels of the vehicle using a pump driven by a motor.
2. Discussion of Related Art
In vehicles, an active suspension system indicates a system in which sensors sense all types of inputs from a road surface and an electronic control unit (ECU) effectively controls the roll behavior of a vehicle based on the sensed inputs.
In detail, an actuator which compensates a displacement of a coil spring connected to a wheel of the vehicle is provided, a fluid quantity supplied to the actuator is appropriately controlled, and changes of the vehicle in rolling and pitching are sensed and a height of the vehicle is constantly maintained, thereby increasing comfortability and a grip force of the vehicle.
In addition, a user may be allowed to set the height of the vehicle depending on wheeling through level-controlling the height of the vehicle or the height of the vehicle may be lowered at a high speed to reduce air resistance, thereby increasing stability in driving and improving fuel efficiency.
U.S. Pat. No. 6,000,702 discloses an active vehicle suspension system which includes a spring and a lift-adjustable regulating unit connected thereto in series, in which a flow of a fluid supplied to the lift-adjustable regulating unit is controlled by a proportional control valve.
However, in such a system described above, the proportional control value and a hydraulic pump are expensive. In addition, the hydraulic pump is connected to an engine and always driven in such a way that the pump is constantly driven while the engine is operating. Accordingly, since the pump is always driven to generate a source of high pressure while the engine is operating, an excessive quantity not needed by the system is necessary and an output of the engine is reduced, thereby having a bad effect on fuel efficiency.